In a court hearing... attorneys for petroleum giants told a San Francisco federal judge...that human activities are clearly responsible for global warming, but that the science isn’t sophisticated enough to point fingers at big oil.  Five oil companies...argued that because the heating of the planet is a “collective” problem, legal efforts...are misguided.  U.S. District Judge William Alsup ordered the unusual climate “tutorial” to better understand a pair of lawsuits that the cities have filed against the companies...Chevron atttorney Ted Boutrous didn’t dispute that humans are contributing to climate change.  [H]e said Chevron agreed with assessments by the Intergovernmental Panel on Climate Change...Boutrous pointed to uncertainty on the part of the panel and others about how bad sea level rise will be...[A]ttorneys for San Francisco and Oakland...called on three climate scientists to present the cities’ view.  Their outlook was largely consistent with what the oil companies had to say, except their projections were more certain and their accounting of blame ran deeper...Judge Alsup...asked the two sides to answer eight questions about climate change...Attorneys for the oil companies are hoping that Wednesday’s debate is...irrelevant...[T]he firms filed a motion to dismiss the lawsuit on grounds that the case is not an issue for a judge but for regulatory agencies...